Abstract
The limiting current densities in electrodialysis were measured for the rare-earth element solutions including one of lanthanum, praseodymium, neodymium, and yttrium (the single-component systems) and those including two of them and EDTA as a chelator (the multi-component systems). In the single-component systems, the observed values of limiting current densities for single rareearth elements were successfully correlated with the following equation under the experimental conditions studied: Ilim=kC0.80u0.76 where Ilim, k, C, and u are limiting current density, constant, solution concentration, and liquid velocity, respectively. In the multi-component systems, a bent point was observed in the currentdensity vs. cell-voltage curves, in which water dissociation did not occur. At the bent point, the observed fluxes of ionic species transferred through a cation-exchange membrane changed abruptly, which suggested that the bent point corresponded to one of limiting current densities for rare-earth elements. The calculation with the equation, mentioned above, for the single-component systems identified the current density at the bent point as one of the limiting current densities for the rare-earth elements.
